Transformer



March 26, 1929.

' E. N. RAULAND TRANSFORMER Filed March 11, 1926 Patented Mar. '26,1929;

UNITED STATES PATENT OFFICE.

EINAR N. RAULAND, OF RIVER FQREST, ILLINOIS, ASSIGNOR 'IO ALL-AMERICANRADIO CORPORATION, OF CHICAGO, ILLINDIS, A CORPORATION OF ILLINOIS.

TRANSFORMER.

Application filed March 11, 1926.

This invention relates to transformers and particularly to an improvedcasing and construction for audio frequency transformers.

It is the object of the present invention to shield the transformerwindings so as to eliminate intern ction between adjacent transformers,but without reducing the efliciency of the transformer.

The invention will be best understood by reference to the drawings inwhich Fig. 1 is a. side elevation; Fi 2 a front elevation; Fig. 3 avertical cro section along lines 3*?) of Fig. 1; and Fig. 4L a verticalcrosssection along lines 4-dof Fig. 2.

The transformer coil consisting of primary 1 and secondary 1 windings ispro vided on an iron core 2 composed of sub stantially rectangularlaminae 3. Each lamination is provided with two perforations l withinwhich the coil is held, and is slit at 5 so that the coil may be slippedin place. The primary 1 is wound over the secondary winding 1 in orderto reduce the mean turn length of the latter. The distributed capacityis thus reduced to a minimum. The laminations are sheared so that themagnetic leakage and core reluctance maybe as small as possible. A heavygauge of high silicon steel is used whereby maximum iron space isobtained.

The core stands on a platform 6 of sheet metal having a bent-down flange7. On two sides the coil is surrounded by two steel shells 88 which havesuitably bulging portions. The shells 8 are placed on the platform 3 andmay be provided with lugs 9 which. project through the platform and arebent up to hold the shells in place. A plate 10 is provided against thelower surface of platform 6 within the substantially rectangulz'zr spacesurrounecd by flange 7. This plate 10 is so fastened that access to thetransformer is prevented. The upper ends and two sides of shells 8 areflattened against the core 2, strips of insulation 11 being providedbetween the core and the shells. A. substantially U-shaped yoke 19.surrounds the iron core 2 on three sides and completes Serial No.93,843.

the transformer casing. The yoke 12 may be provided with lugs like 9 tohold it against the platform 6 or such lugs may be provided only on theyoke since by means of it shells 8 will be clamped in place. The edgesof the yoke are bent down to form flanges 13 clan'iping the edges ofshells 8. Strips of insulation i i are placed between flange 13 and theof shells 8. The terminals of the coil 1 are brought to the outsidethrough perforated binding screws 15 which are mounted on the sides ofshells 8 and are insulated therefrom by means of discs 16.

By insulating the halves of the steel shell 8. no magnetic circuit willbe formed around the coil in plane perpendicular to its axis. Otherwise,the shell would act as a low resistance turn and decrease the impedanceof the primary. Owing; to the shape of the shell 8 and the location ofthe binding posts 15, the lead wires from the coil windings to the postsmay be short.

l hat I claim is:

In an audio frequency transformer, a core composed of substantiallyrectangular, heavy gauge silicon steel laminae, a coil surround ing partof said core and surrounded by said core. said coil being composed of asecondary winding surrounded by a prin'iary winding,

twosteel shells substantially conforming; in

shape to the core and coil assembly each sh ll having an outwardlybulging portion enclosing said coil and flat portions enclosing; saidcore, binding); posts mounted. on said bulging portion, insulationbetween contiguous portions of said shells and core, a substantiallyttshaped steel yoke surrounding said core on three sides and clampingto- ;z'chcr said shells, insulation between said yoke and shells, and abase on which the ends of contiguous portions of said core and shellsrest. fastened to said yoke.

In testimony whereof, I have signed my name to this specification this8th day of March, 1926.

EINAR N. RAULAND.

